Hermaphroditism promotes mate diversity in flowering plants

Area of Science:

• Plant reproductive biology
• Evolutionary genetics

Background:

• Genetically diverse offspring can enhance parental fitness by reducing sibling competition and improving seedling establishment in varied environments.
• Research on plant mate diversity has primarily focused on maternal (seed-producing) aspects, overlooking the male (pollen-donating) role in hermaphrodites.

Purpose of the Study:

• To investigate mate composition overlap between the male and female reproductive functions within individual hermaphroditic flowers.
• To assess the implications of dual sexual functions for plant reproductive success and the evolution of mating systems.

Main Methods:

• An experimental population of 49 Mimulus ringens plants was established, with each plant reduced to a single flower.
• Following natural pollination by wild bees, parentage of 240 progeny (98% of sampled seeds) was assigned to quantify mate composition for both paternal and maternal functions of each flower.

Main Results:

• Mate composition analysis revealed high genetic diversity for both male and female functions within individual flowers.
• Crucially, almost no shared outcross mates were identified between the paternal and maternal roles of the same flower.

Conclusions:

• The dual sexual roles in Mimulus ringens contribute to a significant increase in overall mate diversity, nearly doubling it.
• This enhanced mate diversity through separate use of sexual functions may be a key factor in maintaining hermaphroditism in plants, even when separate sexes might seem advantageous.